The invention relates to a device for fastening a steering wheel hub on a steering column.
DE 196 16 234 A1 discloses a device for fastening a hub on a shaft, in particular a steering wheel hub on a steering column, by means of a screw engaging transversely in the shaft. The screw is guided in the hub and engages partially in the shaft or the steering column by means of a conical section. The shaft is provided with a serration which is assigned a corresponding toothing in the hub.
In the case of this type of connection, precise manufacturing of the individual connecting parts is required so as to fasten the hub on the shaft in a manner free of play.
EP 0 706 929 A1 discloses a device for fastening a hub on a steering column using a fastening screw running transversely to the steering column, the fastening screw being guided in the hub and having a conical section for the central engagement in a groove in the steering column. In addition, the hub bears against the shaft above and below the groove.
EP 0 088 589 A1 and EP 0 339 380 A1 each disclose a device for the coaxial, rotationally fixed connection of two parts which can be rotated together, a threaded pin which is fastened to a first of the two parts engaging by means of a conical section eccentrically in an assigned groove in the other part.
The invention is based on the object of obtaining a play-free connection between the steering column and the steering wheel hub with less complexity.
In the case of a device for fastening a steering wheel hub on a steering column, a fastening screw which runs transversely to the steering column is guided in the hub and has a conical section for engagement in a channel or groove in the steering column. When the hub bears axially against a stop of the steering column, the axis of the screw is situated, according to the invention, higher than the channel or groove center of the steering column, and the hub bears in a positive-locking manner on the shaft above and below the channel or groove. In this case, the angle of taper of the conical section of the screw is smaller than 12xc2x0 so as to obtain self-locking.
Because the axis of the screw is situated higher, on engagement of the conical part of the screw in the groove of the steering column, the hub is pressed against the stop. This eliminates the axial play. The hub is prevented from tilting about the axis of the screw by means of the positive-locking bearing of the hub against the steering column both above and below the channel or groove in the steering column.
It is expedient for the axis of the screw to be situated 0.5 mm higher than the groove center of the steering column.
In a first embodiment, a toothing is provided between the steering column and the hub above and below the channel or groove, the said toothing being used to produce the positive engagement between the steering column and hub. In this embodiment, the stop is planar or conical.
In a second embodiment, in the fastening region of the hub, the steering column is designed as a prism which is adjoined by a truncated pyramidal section which widens downwards to a larger cross section, the prism and the truncated pyramidal section having the same number of edges which are aligned with one another. The hub has a correspondingly designed receiving opening for producing the positive engagement between the steering column and hub, the truncated pyramidal section constituting the axial stop for the hub in this embodiment.
In a preferred refinement of the second embodiment, the prism and the truncated pyramidal section each have six edges. It is further expedient for the edges to be rounded.
The groove or channel is expediently designed in such a manner that the screw touches the steering column linearly after being locked in place.
It is furthermore expedient for a screw having a right-hand thread to be situated on the right-hand side of the axis of the steering column, as seen in the screwing-in direction of the screw. By this means, the hub is pressed onto the stop of the steering column.
The screw is expediently mounted in cylindrical bearings at both ends of the conical region. Compared to a bearing arrangement in the thread, manufacturing with the same tolerances is made more simple.